As is known, a step-down DC/DC converter receives an input DC voltage and converts it to an output DC voltage. This type of converter is often referred to as a buck converter. A buck converter usually has an efficiency of up to 95% for integrated circuits and is self-regulating making it very useful for providing power in devices such as laptop computers where a relatively large DC voltage, in the range of 12 to 24 volts, is converted down to the few volts used by the devices in the computer system.
The operation of a synchronous buck converter is well known in the art and may be described, very simply, as being implemented with a buck controller, an inductor and two transistors: a high-side transistor and a low-side transistor. The controller alternately turns the transistors off and on to alternately connect the inductor to the source voltage to store energy in the inductor or to discharge the inductor into a load. The transistors operate with a fixed duty cycle D where the low-side transistor is turned on for a 1-D portion of each period.
The operation of such a synchronous buck converter, however, requires that the controller driving the transistors operate such that both transistors are not turned on at the same time. This is accomplished by known control circuitry using a pulse width modulated (PWM) signal to control the transistors.
While it may be known to shut down the operation of the synchronous buck converter when there is no load or the load drops below a certain threshold, the response time of the buck converter to come back to full operation mode, when the load does increase, may be unacceptable and, therefore, compromise performance.